Anti-motion Structure of Column Floater

ABSTRACT

An anti-motion structure of a column floater, being an annular structure surrounding the outer periphery of the bottom of a buoy of the column floater, and an annular radial gap between the two is, or optionally is not, set up. The anti-motion structure is connected to a horizontal roof plate, a horizontal floor plate, an outer annular vertical plate, and an inner annular vertical plate to form an annular box body; and the box body is divided into a plurality of watertight compartments; the horizontal roof plate and/or the horizontal floor plate corresponding to each watertight compartment are provided with damping holes capable of being opened or closed.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation of International ApplicationPCT/CN2019/093408 filed Jun. 27, 2019, which claims benefit of priorityof Chinese application CN201810882470.3 filed on Aug. 6, 2018, both ofwhich are incorporated herein by reference.

FIELD OF INVENTION

The present invention relates to the technical field of offshoreengineering, and, in-particular, to an anti-motion structure of a columnfloater.

BACKGROUND

Bottom damping structure or damping plate (anti-motion structure) of acolumn floater (i.e., a straight cylinder type floating platform) is anannular structure, which surrounds the bottom and the outer periphery ofthe upright buoy or extended cylinder of a column floater. For somecolumn floaters, such as SEVAN's cylindrical FPSO, partial fractures arearranged in the annular anti-motion structure to form an intermittentannular structure in order to install fairleads of mooring legs (usually3 groups). The function of anti-motion structure is to increase addedmass of entrained water, natural period and motion damping, and finallyreduce the motion response of the platform and improve the motionperformance of the platform. Therefore, it is called “anti-motionstructure”. In a word, the anti-motion structure is a very importantstructural component of a column floater. According to the structuralform of the radial cross section of the annular anti-motion structure,the anti-motion structure can be divided into three types: the firsttype is represented by SEVAN's cylindrical FPSO, its anti-motionstructure is airtight box-shaped structure with a relatively smallheight, which is a part of the platform's seawater ballast compartment.The second type refers to the U-shaped and inverted U-shaped structureof the open plate structure proposed by the inventor. The third typerefers to a higher-height closed box structure proposed by the inventor,and the damping holes which can be opened or closed are arranged in theroof plate and the floor plate of the box. When the platform is in thestate of floating and wet towing, all damping holes are closed and theanti-motion structure becomes an airtight floating compartment, or thedamping holes in the roof plate are closed and the damping holes in thefloor plate are opened to form an air-float compartment, both of whichcan provide buoyancy and stability for the platform. During in-placecondition (offshore production or survival conditions) of the platform,all damping holes are opened and seawater is filled inside, which makesthe added mass of entrained water increase, but doesn't make thedisplacement of the platform increase (see PCT/CN2017/085052). Theperformance of heave motion of the column floater is the key point thatmust be paid special attention to. Compare the added mass of entrainedwater and viscous damping, the first type of anti-motion structure hasthe worst performance, in particular, the partial fractures of theanti-motion structure for installing fairlead makes the structureintegrity be destroyed, in addition, as the area of horizontalprojection decreases, the added mass of entrained water of the heavemotion decreases accordingly; the second is the second type; and theoptimal one is the third one. However, the third one also falls short interms of how to increase viscous damping, and there is still much roomfor progress. After repeated analysis and calculation and experimentalresearch found that a case in point where conventional cognition is hardto explain, in order to increase the add mass of the internal entrainedwater, under the condition that the outside diameter of the anti-motionstructure remains unchanged, the height of the structure should bemoderately increased, but the viscous damping of the platformoscillation is reduced. The question is how to increase the height ofanti-motion structure moderately and increase viscous damping at thesame time? What else can be done to increase viscous damping? Viscousdamping is of great significance to effectively reduce the motionresponse of a column floater under once-in-a-century environmentalconditions and improve the platform's motion performance.

For the above reasons, based on the results of the study, the inventorimproved and optimized the above three types of anti-motion structure,and put forward a new concept of “edge extending lath”, and with help ofthe edge extending lath, the viscous damping of the platform and the addmass of the entrained water are increased. At same time, adopting grooveinstead of fracture for installing fairlead, forming a new form ofanti-motion structure, finally overcome existing shortcomings of saidthree types of anti-motion structure, and further improve the motionperformance of the platform.

SUMMARY

The invention discloses an anti-motion structure of a column floater,the anti-motion structure is an annular structure, which surrounds thebottom and outer periphery of the upright buoy or extended cylinder(collectively called “the buoy”) of a column floater, and an annularradial gap is set or optionally not set between them. The structuresketch of the radial cross section of the anti-motion structure is arectangular or trapezoid box, which is watertight to be connected by anhorizontal roof plate, an horizontal floor plate, an outer annularvertical plate and an inner annular vertical plate with each other, andbesides, the annular box-typed structure is divided into a plurality ofwatertight compartments by a plurality of radial vertical partitions; Atleast one of the horizontal roof plate and/or the horizontal floor plateprotrudes outward from the intersection between the horizontal roofplate and the outer annular vertical plate (i.e., the “outer corner lineof the box”) to form an outer edge extending lath. Similarly, for theanti-motion structure with annular radial gap, an inner edge extendinglath can also be provided as an option. In order to install fairleads ofmooring legs on the lower part of the buoy of the column floater withoutdestroying the integrity of the anti-motion structure, a U-shaped groovestructure for installing the fairleads is arranged on the anti-motionstructure's inner side adjacent to the buoy shell, and the groovestructure shall not destroy the water tightness of the watertightcompartment.

Both physical model experiment and computer model calculation show thatin the motion process of the platform, the inner and outer edgeextending laths which are set on the horizontal roof plate and thehorizontal floor plate can change the local flow field, intensify theturbulence and dissipate energy of the local water body, thussignificantly increasing the viscous damping of the platform motion andincreasing the add mass of the entrained water. The groove structure isused to replace the current intermittent fracture structure, which isbeneficial to increase the add mass of the entrained water and ensurethe integrity of the structure. Compared with the current anti-motionstructures, the viscous damping and the add mass of the entrained waterof the anti-motion structure of the present invention are increased, soas to further improve the motion performance of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures described herein are for the purposes of interpretation onlyand are not intended in any way to limit the scope of the presentinvention to be disclosed.

FIG. 1 is the main schematic diagram and partial sectional view of theanti-motion structure of a column floater, showing the basic structureof the anti-motion structure and the connection with the buoy.

FIG. 2 is the enlarged diagram at I in FIG. 1, showing the structurediagram of the first type of outer edge extending lath.

FIG. 3 is a radial local section schematic diagram of the anti-motionstructure, showing the second type of outer edge extending lath.

FIG. 4 is a radial local section schematic diagram of the anti-motionstructure, showing the third type of outer edge extending lath.

FIG. 5 is a radial local section schematic diagram of the anti-motionstructure, showing the fourth type of outer edge extending lath.

FIG. 6 is the radial local section schematic diagram of the anti-motionstructure, showing the fifth type of outer edge extending lath.

FIG. 7 is a radial local section of another anti-motion structure of thepresent invention and a magnified view of the same part as that shown inFIG. 2.

DETAILED DESCRIPTION

The details of the invention can be understood more clearly incombination with the figures and the description of the embodiments ofthe present invention. However, the specific embodiment of the presentinvention described herein, only for the purpose of interpreting thepresent invention, cannot be construed in any way as a limitation of thepresent invention.

The invention discloses an anti-motion structure of a column floater(i.e., a straight cylinder floating platform). See FIG. 1, the columnfloater 1 is floating and positioned on a water surface 2; The columnfloater 1 comprises a topside 11, a buoy 12 at a water surface with ananti-motion structure 13; The buoy 12 comprises only an upright buoy orthe upright buoy with extended cylinder, the extended cylinder comprisestwo forms of fixed extended cylinder and sliding extended cylinder; Theanti-motion structure 13 is an annular structure, which surrounds thebottom and outer periphery of the buoy 12, and an annular radial gap 14is set or optionally not set between them. See FIGS. 2 and 3, Theanti-motion structure 13 comprises a roof plate 131, a floor plate 133under the roof plate 131, an outer annular vertical plate 132 and aninner annular vertical plate 134 in between the outer annular verticalplate 132 and the buoy 12, and said four plates (131˜134) are watertightconnected with each other to form an annular box structure with arectangular or trapezoid radial cross section. (FIG. 1-7 show that thestructure sketch of the anti-motion structure with rectangular typedradial crossing section, and the trapezoidal section is not shown.)Among them, the roof plate 131 and the floor plate 133 intersect withthe outer annular vertical plate 132 respectively to form a roof outercorner line of the box (located on the outer edge of the roof of the boxbody) and a floor outer corner line of the box (located on the outeredge of the floor of the box body). The roof plate 131 and the floorplate 133 intersect with the inner annular vertical plate 134respectively to form a roof inner corner line of the box (located on theinner edge of the roof of the box body) and a floor inner corner line ofthe box (located on the inner edge of the floor of box body), and i. e.,forming four circles of closed corner lines. The radial vertical crosssection of the box body of the anti-motion structure 13 shown in FIG.1-7 is a rectangle, and the vertices of the four corners of therectangle are respectively the points on the closed box corner line. Thegeometric figures of box corner line are also different with thedifferent structural forms of the anti-motion structure 13. But in anycase, the geometry centroid of each corner line is located on thevertical central axis of the buoy 12 and the anti-motion structure's boxbody is rotationally symmetric with the centroid (such as a round orregular polygon corner line), or the anti-motion structure's box body issymmetric anteroposterior and left-right with the axis of therectangular coordinate system described the origin as the centroid(i.e., the vertical central axis of the buoy 12), such as an oval cornerline or a closed geometric figure with parallel straight lines on theleft and right sides and circular or broken line on the front and rearsides. The anti-motion structure 13 is connected with the buoy 12 of thecolumn floater 1 by multiple radial vertical brackets (not shown in theattached figures). The box body is divided into several watertightcompartments by a plurality of radial vertical partitions (not shown inthe attached figures). The horizontal roof plate 131 and/or thehorizontal floor plate 133 of each watertight compartment are providedwith damping holes that can be opened and closed. By opening or closingthe damping holes, the column floater 1 can be met the requirement underdifferent working conditions: When the platform is under conditions offloating and wet towing, all the damping holes are closed, thewatertight compartment of the anti-motion structure 13 becomes a closedbuoyancy module, or the damping holes of the roof plate 131 are closedand the damping holes of floor plate 133 are opened at same time, theinterior of the compartment is filled with air, and the watertightcompartment of the anti-motion structure 13 becomes a closed gas-floatcompartment and buoyancy module. Both types of buoyancy module canprovide buoyancy and stability for floating and wet towing of theplatform. During in-place condition of the platform, the damping holesare opened (the best option is to open all damping holes) and the waterfrom the sea is filled inside the anti-motion structure 13, which makesthe added mass of inside entrained water increase, but doesn't make thedisplacement of the platform increase.

The fundamental difference between the present invention andPCT/CN2017/085052 is: at least one plate of roof plate 131 and floorplate 133 of the anti-motion structure 13 without annular radial gap 14shall be provided with an outer edge extending lath respectively; Theouter edge extending laths are roof edge extending lath 135 and flooredge extending lath 136. Refer to FIG. 1-7, showing the anti-motionstructure 13 with annular radial gap 14, an outer edge extending lathand/or an inner edge extending lath are set separately or simultaneouslyon at least one plate of the roof plate 131 and/or the floor plate 133of the anti-motion structure 13. The outer edge extending laths are roofouter edge extending lath 135 and floor outer edge extending lath 136,while the inner edge extending laths are roof inner edge extending lathand floor inner edge extending lath. The outer edge extending lath is aplate structure, which extends outward and/or upward and/or downwardfrom the roof outer corner line and the floor outer corner linerespectively. The roof outer edge extending lath 135 is formed on theroof plate 131 and the floor outer edge extending lath 136 is formed onthe floor plate 133. The inner edge extending lath is a plate structure,which extends horizontally from the roof inner corner and/or the floorinner corner of the box to the direction of the buoy 12. The horizontalroof inner edge extending lath is formed on the roof plate 131, and thehorizontal floor inner edge extending lath is formed on the floor plate133. The inner edge extending lath shall not close the annular radialgap 14 (See FIG. 7).

As a practical embodiment, the anti-motion structure 13 is a circular ora regular polygon structure, and the four box corner lines correspond toa circular or a regular polygon. As another practicable embodiment, theshape of the inner wall (the inner annular vertical plate 134) and theouter wall (the outer annular vertical plate 132) of the annularanti-motion structure of the present invention is different. Forexample, the inner wall is a circular of ring plate or positivemultilateral ring plate, and the roof inner corner line of the box andthe floor inner corner line of the box are corresponding to a circularor regular polygon, and the outer wall is oval-shaped, and the roofouter corner line and the floor outer corner line of the box is an oval;or the outer wall is hetero-polygons-shaped, the roof outer corner linesand the floor outer corner line of the box is a closed geometric figuresformed by parallel straight lines on the left and right sides andcircular or broken lines on the front and rear sides, the dimensions inthe left and right directions are smaller than those in the front andrear directions. Its advantage is that the requirements of width ofdrydock for platform construction of can be reduced.

Further, the roof outer edge extending lath 135 and the floor outer edgeextending lath 136 are of annular plate structures. The end edge of roofouter edge extending lath 135 and the end edge of the floor outer edgeextending lath 136 form a roof outer end edge line and a floor outer endedge line respectively. The geometric figures of said two end edge lineshave the same centroid as the roof outer corner line and the floor outercorner line of the box, which is rotationally symmetric with thecentroid or symmetric with the vertical central axis of the buoy 12 indirection of anteroposterior/left-right. Or, the roof outer edgeextending lath 135 and the floor outer edge extending lath 136 areprotruding to form a wall structure upward and downward respectively,and the upper edge and lower edge of the protruding edge extending lathwall structure form a circle of closed upper end edge line and a circleof closed lower end edge line respectively. The centroid of the geometryof said each end edge line is located in the vertical central axis ofbuoy 12 and equal to or similar to the geometry of the roof and floorcorner lines of the box respectively; or the roof outer edge extendinglath 135 and the floor outer edge extending lath 136 is an horizontalannular plate then folding and protruding upward or downward to form awall structure respectively, and the end edge of the wall of the roofouter edge extending lath 135/the floor outer edge extending lath 136forms a circle of closed roof/floor end edge line respectively. Thecentroid of the plane geometry of the circle of closed roof/floor endedge line is located in the vertical central axis of the buoy 12, whichis similar to the plane geometry of the roof outer corner line of thebox/the floor outer corner line of the box. Alternatively, the roofouter edge extending lath 135/the floor outer edge extending lath 136consists of a horizontal annular plate structure plus a vertical ringwall structure protruding upward/downward respectively; and in suchcase, the roof outer edge extending lath 135 forms a circles of roofouter end edge line plus a circle of roof upper end edge line, and thefloor outer edge extending lath 136 forms a circles of floor outer endedge line plus a circle of floor lower end edge line, i.e., both of theroof outer edge extending lath 135 and the floor outer edge extendinglath 136 have two circles of end edge lines.

Further, roof outer edge extending lath 135 and floor outer edgeextending lath 136 are single-layer plate structures (see FIGS. 1-7).For the convenience of description and understanding, the platethickness of the edge extending lath structure is very small, and theplate thickness is ignored in the following description of the inventionand regarded as “paper”. Therefore, as the edge extending lath with aconvex structure extending up and down (see FIG. 3˜6), said convexstructure of the roof outer edge extending lath 135 and the floor outeredge extending lath 136 will form an upright frustum cone wall or anupright cylindrical wall (see FIG. 3 and FIG. 5), or form a horizontalannular plate structure then folding and protruding upward or downwardbeing a convex structure (see FIG. 4 and FIG. 6), said convex structureforms a circle of closed upper end edge line and a circle of closedlower end edge line, which centroid of the geometry is located in thevertical central axis of the buoy 12 and which geometry is equal to orsimilar to the geometry of the roof and floor corner lines of the boxrespectively. When the outer edge extending laths are as shown as FIGS.1/2/7 being horizontal extension structures of the roof plate 131 and/orthe floor plate 133, both of the roof outer edge extending lath 135 andthe floor outer edge extending lath 136 are horizontal annular platesand each plate with only one closed circle outer end edge line (theinner edge line is merged with the outer box corner line).

Optionally, multiple damping holes can be set or not be set on the roofouter edge extending lath 135 and the floor outer edge extending lath136.

The outer edge extending lath (i.e., the roof outer edge extending lath135 and/or the floor outer edge extending lath 136) comprises sixstructural forms.

(1) The roof outer edge extending lath 135 or the floor outer edgeextending lath 136, as horizontal annular plate structures, are thehorizontal extension structures of the roof plate 131 or the floor plate133 respectively, and the geometries of their outer end edge lines (i.e., the outer end edge line of the roof outer edge extending lath 135and the outer edge line of the floor outer edge extending lath 136) havethe same centroid as the geometries of the roof corner line of the boxand the floor corner line of the box, and are rotationally symmetricalwith the centroid, or anteroposterior and left-right symmetrical withthe axes of the Cartesian coordinate system with the centroid as theorigin, as shown in FIGS. 1, 2 and 7.

(2) The roof outer edge extending lath 135 is an inverted frustum-shapedwall structure with its upper dimension larger than its lower dimension,which lower end edge line coincides with the roof outer corner line ofthe box; and the floor outer edge extending lath 136 is a positivefrustum-shaped wall structure with its upper dimension less than itslower dimension, which upper end edge line coincides with the floorouter corner line of the box, see FIG. 3.

(3) The roof outer edge extending lath 135 or the floor outer edgeextending lath 136 is a horizontal annular plate as the extensionstructure of the roof plate 131 or the floor plate 133 (the extensiondistance is smaller), and then folded upward to form an invertedfrustum-shaped wall structure with its upper dimension larger than itslower dimension or downward to form a positive frustum-shaped wallstructure with its upper dimension less than its lower dimensionrespectively. The dimension of the lower edge line graph of the invertedfrustum-shaped wall structure is larger than that of the roof outercorner line graph of the box, and said two graphs are similar figureswith a common centroid; the dimension of the upper edge line graph ofthe positive frustum-shaped wall structure is larger than that of thefloor outer corner graph of the box, and said two graphs are similarfigures with a common centroid, see FIG. 4.

(4) The roof outer edge extending lath 135 is a vertical cylindricalwall structure by folding the horizontal roof plate 131 upward with a90-degree angle on the roof outer corner line of the box, and the floorouter edge extending lath 136 is a vertical cylindrical wall structureby folding the horizontal floor plate 133 downward with a 90-degreeangle on the floor outer corner line of the box; the lower edge line ofthe vertical cylindrical wall structure of the roof outer edge extendinglath 135 coincides with the roof outer corner line of the box, and theupper edge line of the vertical cylindrical wall structure of the floorouter edge extending lath 136 coincides with the floor outer corner lineof the box, see FIG. 5.

(5) The roof outer edge extending lath 135 or the floor outer edgeextending lath 136 is a horizontal annular plate as the extension plateof the roof plate 131 or the floor plate 133 (the extension distance issmaller), and then connected with a vertical cylindrical wall structureby folding the horizontal extended plate upward or downward with a90-degree angle respectively. The dimension of the lower edge line graphof the vertical cylindrical wall structure of the roof outer edgeextending lath 135 is larger than that of the roof outer corner linegraph of the box, and said two graphs are similar figures with a commoncentroid. The dimension of the upper edge line graph of the verticalcylindrical wall structure of the floor edge extending lath 136 islarger than that of the floor outer corner graph of the box, and saidtwo graphs are similar figures with a common centroid, see FIG. 6.

(6) A combination of the above-mentioned two structural forms (1) and(4), the roof outer edge extending lath 135 or the floor outer edgeextending lath 136 is a horizontal extension plate extending from theroof plate 131 or the floor plate 133, and at the same time, plus avertical cylindrical wall structure connected upward to the roof outercorner line of the box or downward to the floor outer line of the boxwith a 90-degree angle from the horizontal extension plate; thus theroof outer edge extending lath 135 or the floor outer edge extendinglath 136 both has two circles of end edge lines, i.e., a circle of roofouter end edge line plus a circle of roof upper end edge line, and acircle of floor outer end edge line plus a circle of floor lower endedge line respectively (not shown in the figures).

In order to understand the convex edge extending lath structure moreclearly, taking the doughnut-shaped anti-motion structure with saidthird form of edge extending lath structure (the radial cross section isrectangular) as an example to give description: Under the aboveconditions, the four corner lines of the box of the anti-motionstructure are all round, and the center of the four circles are locatedin the vertical central axis of buoy 12, the roof outer edge extendinglath 135 or the floor outer edge extending lath 136 is formed by ahorizontal extension plate of the roof plate 131 or the floor plate 133firstly, and then folding the extension plate upward or downward as aninverted circular truncated cone with its upper diameter larger than itslower diameter or a positive circular truncated cone with its upperdiameter less than its lower diameter respectively, and the lowerdiameter of the inverted circular truncated cone is larger than diameterof the circle of the roof outer corner line with a common circle centerand the upper diameter of the positive circular truncated cone is largerthan diameter of the circle of the floor outer corner line with a commoncircle center.

Although FIG. 1˜6 shows that the roof outer edge extending lath 135 andthe floor outer edge extending lath 136 adopt a combination of the samestructural form, the roof outer edge extending lath 135 and the floorouter edge extending lath 136 can adopt a different combinationaccording to different demands. For example, the roof outer edgeextending lath 135 adopts the second form of structure (shown in FIG. 3)and the floor outer edge extending lath 136 adopts the first form ofstructure (shown in FIG. 2), etc. The protruding size of the edgeextending lath (the roof outer edge extending lath 135 and the floorouter edge extending lath 136) is smaller compared to the size ofanti-motion structure 13. The specific size of the edge extending lathof plate structure, whether damping holes setting up on the edge plateor not, and the number and diameter of the damping holes should bedetermined and optimized by experiment and calculation.

For the anti-motion structure 13 with annular radial gap 14, as anoptimized embodiment of the present invention, a horizontal annularplate is arranged on at least one annular part on the outer wall of buoy12 which is the same as the elevation of the roof plate 131 and/or thefloor plate 133, thus a buoy upper lath 121 and/or a buoy lower lath 122(see FIG. 7) are formed with a gap between the buoy upper lath 121 andthe roof inner edge extending lath and/or with a gap between the buoylower lath 122 and the floor inner edge extending lath respectively tofurther increase the damping of heave motion. Another embodiment toincrease the damping of the heave motion is presented below, for theanti-motion structure 13 with annular radial gap 14, at least one plateof the roof plate 131 and the floor plate 133 shall extend horizontallyin the direction of buoy 12 from the roof inner corner line of the boxand/or from the floor inner corner line of the box up to connecting thebuoy 12 respectively to close the annular radial gap 14, and a pluralityof damping holes are set up on the closing area of the gap, usuallyevenly distributed (not shown in the figures). In order to furtherincrease damping, as an optimal embodiment, the upper gap between theroof inner edge extending lath and the buoy upper lath 121 and the lowergap between the floor inner edge extending lath and the buoy lower lath122 should be dislocated as far as possible. For example, the upper gapis closer to the buoy 12 and the lower gap is closer to the innerannular vertical plate 134. Or further, adding a layer of horizontalinterspace annular plate at the midpoint between the roof inner edgeextending lath and the floor inner edge extending lath, which is mountedon the inner annular vertical plate 134 or on the outer wall of the buoy12 and maintains a gap with the outer wall of the buoy 12 or with theinner annular vertical plate 134 (both called “middle gap”)respectively, thus making the upper gap, lower gap and middle gapdislocation of each other. The gap dislocation, especially thehorizontal interspace annular plate can not only increase the viscousdamping, but also lessen the mass reduction of the entrained water dueto the gap between the anti-motion structure 13 and the buoy 12.

As a further optimal embodiment, said outer end edge line (the roofouter end edge line or the floor outer end edge line) can adopt aserrated line to replace a flat straight line or smooth arc line, thatis, a serrated end edge with tooth convex and tooth concave to replacethe straight or smooth curved end edge, and the tooth convex and thetooth concave have the same or different geometric figures. That is tosay, when both roof outer edge extending lath 135 and floor outer edgeextending lath 136 are horizontal annular plates, one of the roof outerend edge line and/or the floor outer end edge line is at least onecontinuous serrated line, and/or one of the roof inner end edge line andthe floor inner end edge line is at least a continuous serrated line.The serrated edge on each tooth is usually described as a regulargeometric figure, such as triangular tooth, rectangular or trapezoidaltooth; and the convex and concave shapes of triangular teeth aretriangular, the convex and concave shapes of the rectangular teeth arerectangular, or the convex and concave shapes of the trapezoidal teethare trapezoidal, and the convex and concave shapes of the s are acombination of triangle, rectangular and/or trapezoidal; Or the serratededge on each tooth is an irregular geometric figure, of which the convexand concave shapes of the teeth are other figures different fromtriangle, rectangle or trapezoid. For example, for the roof outer edgeextending lath 135 and the floor outer edge extending lath 136 withmultiple damping holes, a notch from the end edge of the edge extendinglath to each damping hole is set up to form a convex and concave oftooth.

As another further optimal embodiment, said roof upper end edge line orsaid floor lower end edge line can adopt a serrated line to replace aflat straight line or smooth arc line, that is, a serrated end edge withtooth convex and tooth concave to replace the straight or smooth curvedend edge, and the tooth convex and the tooth concave have the same ordifferent geometric figures. That is to say, when the roof outer edgeextending lath 135 or the floor outer edge extending lath 136 extendingup or down to form a closed circle roof upper end edge line or a closedfloor circle lower end edge line, one of the roof upper end edge lineand/or the floor lower end edge line is at least a continuous serratedline. The serrated edge on each tooth is usually described as a regulargeometric figure, such as triangular tooth, rectangular or trapezoidaltooth; and the convex and concave shapes of the triangular teeth aretriangular, the convex and concave shapes of the rectangular teeth arerectangular, or the convex and concave shapes of the trapezoidal teethare trapezoidal, and the convex and concave shapes of the compound teethare a combination of triangle, rectangular and/or trapezoidal; Or theserrated edge on each tooth is an irregular geometric figure, of whichthe convex and concave shapes of the teeth are other figures differentfrom triangle, rectangle or trapezoid. For example, for the roof outeredge extending lath 135 and the floor outer edge extending lath 136 withmultiple damping holes, a notch from the end edge of the edge extendinglath to each damping hole is set up to form a convex and concave oftooth.

Compared with a straight or smooth curved end edge, the edge extendinglath with an end edge line shaped the convex and concave of teeth willfurther increase the viscous damping of the platform motion.

As an optimized embodiment, for the roof outer edge extending lath 135and/or the floor outer edge extending lath 136 of the anti-motionstructure being horizontal annular plate, when the roof outer end edgeline and the floor outer end edge line adopt serrated lines, or when theroof outer edge extending lath 135 and floor outer edge extending lath136 are set up damping holes, a layer of horizontal interspace annularplate at the midpoint between the roof outer edge extending lath and thefloor outer edge extending lath, namely middle outer edge extendinglath, is mounted on the outer annular vertical plate 132, and the endedge of the middle outer edge extending lath is a straight and/or smoothcurved edge line. The function of the middle outer edge extending lathis to reduce the loss of add mass of the entrained water of heave motiondue to the serrated edges and/or damping holes of the roof outer edgeextending lath 135 and floor outer edge extending lath 136.

In order to install fairleads of mooring legs at the lower part of theouter wall of the buoy 12 without destroying the integrity of theanti-motion structure and to increase the add mass of the entrainedwater, at the position on the inner side of anti-motion structure 13adjacent to the buoy 12 and corresponding to the space for installingfairlead, a U-shaped fairlead groove is set up horizontally and up anddown through the roof plate and the floor plate (not shown in thefigures). The structure of said each U-shaped groove is as follows: theinner annular vertical plate 134 corresponding to the U-shaped groovecovering area is shifted outwards (in the horizontal direction away fromthe buoy 12), and vertical baffles are installed on both sides of theU-shaped groove; the plate surface of the roof plate 131 and the floorplate 133 covered by the U-shaped groove are excised except that theU-shaped edge is retained to form a U-shaped plate edge extending lath.A total of 5 pieces of plates, i.e., said shifted inner annular verticalplate, said vertical baffles on both sides of the groove and said roofplate 131 and floor plate 133 taken some areas out, are watertightconnected with each other. In other words, the water tightness of thewatertight compartments of the anti-motion structure shall not bedestroyed after the U-shaped fairlead groove been formed. The so-calledU-shaped plate edge extending lath refers to the U-shaped edges of thehorizontal roof plate 131 and the floor plate 133 protruding from theshifted part of the inner annular vertical plate and the verticalbaffles on both sides of the groove. The U-shaped plate edge extendinglath is good for viscous damping. The space of the groove must becapable of accommodating the fairlead mounted below the buoy 12 andensuring necessary maintenance requirements. As a practical embodiment,the fairlead groove of the anti-motion structure 13 was broken as afracture at the initial stage of construction, and after the fairleadguide groove been installed to the buoy 12, a water-tight box structureare installed to close the fracture to form a complete U-shaped fairleadgroove.

The present invention overcomes the shortcomings of the currentanti-motion structure of column floater, not only increases the add massof the entrained water, but also increases the damping of motions,especially the damping of heave motion, at the same time ensures theintegrity of anti-motion structure, and finally greatly improves themotion performance of the column floater.

1. An anti-motion structure of a column floater comprising: an annularstructure surrounding the bottom and outer periphery of the buoy of thecolumn float, said annular structure comprises a roof plate, a floorplate with spacing below the roof plate, an outer annular vertical plateand an inner annular vertical plate spaced between the outer annularvertical plate and the buoy, and said roof plates, floor plate, outerannular vertical plate and inner annular vertical plate to be watertightconnected with each other to form an annular box with rectangular ortrapezoidal radial vertical cross section, and to form a total of fourcircles of corner lines along the box corners, i.e., a roof outer cornerline of the box, a floor outer corner line of the box, a roof innercorner line of the box and a floor inner corner line of the box, whereinthe centroid of each corner line of plane geometry is located in thevertical central axis of the buoy and the said annular box body isrotationally symmetric with the centroid, or symmetric anteroposteriorand left-right with the vertical central axis of the buoy, and anannular radial gap is set or optionally not set between the anti-motionstructure and the buoy; wherein the anti-motion structure is connectedwith the buoy by multiple radial vertical brackets, and the box body isdivided into several watertight compartments by a plurality of radialvertical partitions, the horizontal roof plate and/or the horizontalfloor plate corresponding to each watertight compartment are providedwith damping holes capable of being opened or closed; by opening of thedamping holes in the horizontal roof plate and the horizontal floorplate, the compartments are filled with water introduced with sea, or byclosing of the damping holes in the horizontal roof plate and thehorizontal floor plate, a closed floating compartment is formed, or byclosing of the damping holes in the horizontal roof plate and opening ofthe damping holes in the horizontal floor plate, a closed air floatingcompartment is formed, so as to meet requirements under differentworking conditions of the column floater; wherein at least one of platesof the roof plate and/or the floor plate of the anti-motion structurewithout the annular radial gap shall be provided with an outer edgeextending lath, i.e., roof outer edge extending lath and floor outeredge extending lath; and at least one of plates of the roof plate andthe floor plate of the anti-motion structure with the annular radial gapshall be provided with an outer edge extending lath and an inner edgeextending lath separately or simultaneously, said outer edge extendinglath is the outer edge extending lath and the floor outer edge extendinglath, and said inner edge extending lath is roof inner edge extendinglath and floor inner edge extending lath; wherein the outer edgeextending lath is a plate structure, which extends outward and/or upwardand downward from the roof outer corner line and the floor outer cornerline respectively; the roof outer edge extending lath is formed on theroof plate and the floor outer edge extending lath is formed on thefloor plate; the inner edge extending lath is a plate structure, whichextends horizontally from the roof inner corner line and/or the floorinner corner line of the box to the direction of the buoy; thehorizontal roof inner edge extending lath is formed on the roof plate,and the horizontal floor inner edge extending lath is formed on thefloor plate; the inner edge extending lath shall not close the annularradial gap.
 2. The anti-motion structure of column floater according toclaim 1 comprising: the anti-motion structure is a circular or regularpolygon structure, and the four box corner lines correspond to acircular or regular polygon; or the shapes of the inner annular verticalplate and the outer annular vertical plate of the anti-motion aredifferent, the inner annular vertical plate is circular or regularpolygon and the roof inner corner line and the floor inner corner lineof the box are circular or regular polygon accordingly, and the outerannular vertical plate is oval and the roof outer corner line and thefloor outer corner line of the box are oval accordingly, or the outerannular vertical plate is hetero-polygon, the roof outer corner line andthe floor outer corner line of the box are closed geometric figures withparallel straight lines on the left and right sides and circular orbroken lines on the front and rear sides, its dimensions in the left andright directions are smaller than those in the front and reardirections.
 3. The anti-motion structure of column floater according toclaim 2 comprising: the roof outer edge extending lath and the floorouter edge extending lath are of horizontal annular structures, the edgeof the roof outer edge extending lath and the edge of the floor outeredge extending lath forms a roof outer end edge line and a floor outerend edge line respectively; and the plane geometric figures of the roofouter edge line or the floor outer edge line has the same centroid asthe roof outer box corner line and the floor outer box corner line andis rotationally symmetric to the centroid, or symmetric to the verticalcentral axis of the upright floater front-back and left-right; or, theroof outer edge extending lath or the floor outer edge extending lath isa protruding wall structure upward or downward respectively, and theupper edge and the lower edge of each protruding edge extending lathwall structure form a circle of closed upper end edge line and a circleof closed lower end edge line respectively, which centroid is located inthe vertical central axis of buoy and the geometry of said each end edgeline is equal to or similar to the geometry of the roof and floor cornerlines of the box respectively; or the roof outer edge extending lath orthe floor outer edge extending lath is an horizontal annular plate thenfolding and protruding upward or downward to form a wall respectively,and the end edge of the wall of the roof outer edge extending lath or ofthe floor outer edge extending lath forms a circle of closed roof endedge line or a circle of closed floor end edge line respectively, whichcentroid of the plane geometry is located on the vertical central axisof the buoy, and the plane geometry of the circle of closed roof endedge line or the circle of closed floor end edge line is similar to theplane geometry of the roof outer corner line of the box or similar tothe plane geometry of the floor outer corner line of the boxrespectively.
 4. The anti-motion structure of column floater accordingto claim 3 comprising: the roof outer edge extending lath or the floorouter edge extending lath is a horizontal annular plate structure, whichis the horizontal and outward extension structure of the roof plate orthe floor plate; or the roof outer edge extending lath is an invertedfrustum-shaped wall structure with its upper dimension larger than itslower dimension, which lower end edge line coincides with the roof outercorner line of the box; and the floor outer edge extending lath is apositive frustum-shaped wall structure with its upper dimension lessthan its lower dimension, which upper end edge line coincides with thefloor outer corner line of the box; or the roof outer edge extendinglath or the floor outer edge extending lath is a horizontal and outwardextension structure of the roof plate or of the floor plate with limitedextending distance, and then connected to an inverted frustum-shapedwall structure with its upper dimension larger than its lower dimensionor to a positive frustum-shaped wall structure with its upper dimensionless than its lower dimension respectively; at same time the dimensionof the circle of closed lower end edge line graph of the invertedfrustum-shaped wall structure is larger than that of the roof outercorner line graph of the box, and said two graphs are similar figureswith a common centroid, and the dimension of the circle of closed upperend edge line graph of the positive frustum-shaped wall structure islarger than that of the floor outer corner graph of the box, and saidtwo graphs are similar figures with a common centroid; or the roof outeredge extending lath or the floor outer edge extending lath is a verticalcylindrical wall structure by folding the horizontal roof plate upwardor the horizontal floor plate downward with a 90-degree angle on theroof or floor outer corner line of the box respectively; the lower edgeline of the vertical cylindrical wall structure of the roof outer edgeextending lath coincides with the roof outer corner line of the box, andthe upper edge line of the vertical cylindrical wall structure of thefloor outer edge extending lath coincides with the floor outer cornerline of the box; or the roof outer edge extending lath or the floorouter edge extending lath is a horizontal and outward extensionstructures of the roof plate or of the floor plate with some extendingdistance, and then connected to a vertical cylindrical wall structure byfolding the extension structure upward or downward with a 90-degreeangle respectively; the dimension of the lower edge line of the verticalcylindrical wall structure of the roof outer edge extending lath islarger than the roof outer corner line of the box, and the dimension ofthe upper edge line of the vertical cylindrical wall structure of floorouter edge extending lath is larger than the floor outer corner line ofthe box, and said two graphs are similar figures with a common centroid.5. The anti-motion structure of column floater according to claim 1comprising: some damping holes are set up or optionally not set up onthe roof outer edge extending lath and/or floor outer edge extendinglath.
 6. The anti-motion structure of column floater according to claim5 comprising: for the anti-motion structure with annular radial gap, ahorizontal annular plate is arranged on at least one part of the annularpart on the outer wall of the buoy which is the same elevation as theroof plate and/or the floor plate, thus a buoy upper lath and/or a buoylower lath are formed with a gap between the buoy upper lath and theroof inner edge extending lath and/or between the buoy lower lath andthe floor inner edge extending lath.
 7. The anti-motion structure ofcolumn floater according to claim 5 comprising: at least one of the roofplate and the floor plate of the anti-motion structure with the annularradial gap shall extend horizontally in the direction of the buoy fromthe roof inner corner line of the box and the floor inner corner line ofthe box up to connecting the buoy respectively to close the annularradial gap, and a plurality of damping holes are set up on the closingarea the gap.
 8. The anti-motion structure of column floater accordingto claim 1 comprising: a U-shaped fairlead groove is set up horizontallyand up and down through the roof plate and the floor plate at theposition on the inner side of anti-motion structure) adjacent to thebuoy and corresponding to the space for installing fairlead, which shallbe capable of accommodating and facilitating the maintenance of thefairlead mounted on the lower part of the outer wall of the buoy; thestructure of said each U-shaped groove is as follows: the inner annularvertical plate corresponding to the U-shaped groove covering area isshifted outwards, and vertical baffles are installed on both sides ofthe U-shaped groove; the plate surface of the roof plate and the floorplate covered by the U-shaped groove are excised except that theU-shaped edge is retained to form a U-shaped plate edge extending lath;said shifted inner annular vertical plate, said vertical baffles on bothsides of the groove and said roof plate and floor plate been taken someareas out are watertight connected to each other, and the watertightness of the watertight compartments of the anti-motion structureshall not be destroyed after the U-shaped fairlead groove been formed.9. The anti-motion structure of column floater according to claim 3comprising: when both roof outer edge extending lath and floor outeredge extending lath are horizontal annular plates, one of the roof outerend edge line and/or the floor outer end edge line is at least onecontinuous serrated line to form a serrated end edge, and/or one of theroof inner end edge line and/or the floor inner end edge line is atleast a continuous serrated line to form a serrated end edge; when bothroof outer edge extending lath and floor outer edge extending lath witha convex structure extending up and down to form a closed circle roofupper end edge line and a closed floor circle lower end edge line, atleast one of the roof upper end edge line and/or the floor lower endedge line is a continuous serrated line to form a serrated end edge;said serrated end edge with tooth convex and tooth concave, which havethe same or different geometric figures.
 10. The anti-motion structureof column floater according to claim 9 comprising: said serrated edge oneach tooth is triangular tooth, rectangular or trapezoidal tooth, andthe shape of the convex and concave teeth of triangular teeth istriangular, the convex and concave shapes of the rectangular teeth arerectangular, the convex and concave shapes of the trapezoidal teeth aretrapezoidal, and the convex and concave shapes of the compound shapedteeth are respectively a combination of triangle, rectangle ortrapezoidal.
 11. The anti-motion structure of column floater accordingto claim 3 comprising: the roof outer edge extending lath or the floorouter edge extending lath is a horizontal annular plate extending fromthe roof plate or the floor plate respectively, and at the same time,plus a vertical cylindrical wall structure connected upward to the roofouter corner line of the box or downward to the floor outer line of thebox with a 90-degree angle from the horizontal extension plate; the roofouter edge extending lath or the floor outer edge extending lathsimultaneously form a circle of roof outer end edge line plus a circleof roof upper end edge line, or a circle of floor outer end edge lineplus a circle of floor lower end edge line respectively.
 12. Theanti-motion structure of column floater according to claim 4 comprising:for the roof outer edge extending lath and floor outer edge extendinglath of anti-motion structure being horizontal annular plates, when theroof outer edge line and the floor outer edge line adopt serrated lines,or when the roof outer edge extending lath and the floor outer edgeextending lath are provided with damping holes, a middle outer edge lathis arranged on the outer annular vertical plate equidistant from theroof outer box corner line and the floor outer box corner line, themiddle outer edge lath is a horizontal annular plate structure, and itsouter end edge is a straight and/or smooth curved edge.
 13. Theanti-motion structure of column floater according to claim 6 comprising:the upper gap between the roof inner edge extending lath and the buoyupper lath and the lower gap between the floor inner edge extending lathand the buoy lower lath should be dislocated as far as possible; orfurther, adding a layer of horizontal interspace annular plate at themidpoint between the roof inner edge extending lath and the floor inneredge extending lath, which is mounted on the inner annular verticalplate and maintains a middle gap with the outer wall of the buoy, ormounted on the outer wall of the buoy and maintains a middle gap withthe inner annular vertical plate, thus the upper gap, the lower gap andthe middle gap are dislocated with each other.